The present invention relates to a skew motor driving circuit for satellite video receiver (SVR), and more particularly to a skew motor driving circuit of satellite video receiver for eliminating a skew pulse noise upon fine movement of the skew motor of SVR.
In a satellite communication system of satellite video and the like, supper high frequency signal SHF transmitted from a satellite is received by a parabola antenna, which is low-noise-amplified by a low noise block down converter LNB whereby sent to a receiver which is set at indoor.
Since a radio wave corresponding to each video channel is incident to a parabola antenna and LNB at a predetermined angle, the radio wave corresponding to each video channel is received by changing an angle of probe provided within the LNB. In order to change the angle of probe, the skew motor is provided to LNB.
Heretofore, the skew motor driving circuit of SVR was constructed as shown in FIG. 1.
Firstly, a skew motor driving power source of a power supply section is connected to an emitter of a transistor Q1 and it is so connected to a base that a power control signal outputted from a control section 1 is inputted through a resistor R1, and a power terminal (+) of the skew motor 3 is connected to a collector at the same time it is grounded through a resistor R2.
On the other hand, it is so connected that a skew pulse outputted from the control section 1 is inputted to a base of transistor Q2 through a resistor R5, an emitter is grounded, a collector is connected to +5 V power through a resistor R4 and at the same time connected to an input terminal S of the skew motor 3, and a ground terminal (-) of the skew motor 3 is grounded.
And, the collector of the transistor Q2 is connected with a resistor R3 in parallel and grounded. In a conventional skew motor driving circuit as this, when a power control signal inputted from the control section 1 is "high", the transistor becomes off and when it is "low" then it becomes on.
When the transistor Q1 becomes on, an inputting power +6 V supplied from the power supply section is supplied to a power terminal (+) of the skew motor 3.
At this moment, in response to a skew pulse signal inputted from the skew terminal of the control section, when the pulse signal is "high", the transistor Q2 becomes on, and when it is "low", it becomes off. The skew pulse is inputted to the input terminal S of the skew motor 3 in accordance with on/off of the transistor Q2. Thus, when the skew pulse is inputted to the skew motor 3 through the transistor Q2 at a state that a power of +6 V is applied to a power terminal (+) of the skew motor 3, the skew motor 3 is rotated in proportion to number of the skew pulses and makes the probe of LNB (+) to be rotated to a predetermined angle whereby makes to move to a receiving location for receiving a frequency of particular channel in optimum.
However, thus in a conventional technique, after the LNB 4 takes an exact position by the skew motor 3, when the skew pulses are continuously applied to the transistor Q2 at a state that the transistor Q1 becomes off and the driving power is not applied to the skew motor 3, as shown in FIG. 1, a remaining voltage being close to ripple is generated to the power terminal (+) of the skew motor 3 and thereby a problem is occurred that the skew motor 3 makes error operation.
In accordance with influence of the ripple remaining voltage, there has been much problems of ill influenced to a remocon operation for controlling the skew motor and generating a shaking phenomenon on a screen.